Food allergy a risk factor for oral allergy syndrome among children with allergic rhinitis
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Food allergy and food sensitization in early childhood appeared associated with oral allergy syndrome among children with allergic rhinitis, according to a study published in Pediatric Allergy and Immunology.
Children with a history of early childhood food allergy should be monitored for oral allergy syndrome symptoms before age 6 years, Kun-Baek Song, clinical assistant professor in the department of pediatrics at Soonchunhyang University Hospital in Cheonan, South Korea, and colleagues wrote.
The study involved 930 children aged older than 6 years (average age, 8.02 years; 52.7% boys) from the cohort for childhood origin of asthma and allergic diseases, a prospective, general population-based birth cohort study.
Children and their mothers participated in regular follow-up visits with a physician examination and self-reported environmental questionnaires at a minimum of 26 weeks’ gestation, at birth, at 6 months and at 1 year, and annually thereafter.
According to the researchers, 44 children (4.7%) had oral allergy syndrome (OAS), defined as a hypersensitivity reaction to specific foods caused by prior sensitization to inhalant pollen allergens, with a mean age of onset of 6.74 years. Typical symptoms of OAS — which is triggered by fresh fruits and vegetables that cross-react with pollen — include itching, sore throat or swelling in the lips, mouth and throat.
Also, 48.9% of patients had allergic rhinitis (AR), 16.5% had allergic conjunctivitis (AC), 47.8% had any atopy and 11% had pollen sensitization.
Across the study population, 7.2% of children with AR and 19.1% of children with pollen sensitization had OAS.
The most prevalent OAS triggers included: fruits at 47.7%, the most common being kiwi (22.7%) and peach (11.4%); vegetables at 27.3%, the most common being tomato (18.2%) and watermelon (9.1%); and nuts at 9.1%, the most common being peanut (6.8%).
A greater proportion of children with OAS had AR (75.6% vs. 47.6%; P = .001) and atopic dermatitis (AD; 31.7% vs. 15.9%; P = .016) than those without OAS. However, the researchers did not find a significant difference in asthma incidence between the groups (7.3% vs. 5%).
When aged 6 to 7 years, the children with OAS had a significantly higher sensitization rate to birch (34.4% vs. 5%), alder (12.5% vs. 3.3%), Japanese hop (12.5% vs. 1.9%), oak (18.8% vs. 6%) and ragweed (6.3% vs. 0.9%; P < .05 for all) compared with those without OAS, although there was no significant difference between the groups in sensitization to food and indoor or other outdoor allergens.
The researchers further found an association between OAS and food allergy (adjusted OR = 3.803; 95% CI, 1.795-8.057) and AD at age 1 to 3 years (aOR = 2.393; 95% CI, 1.243-4.609).
Based on serum-specific IgE at age 1 year, a greater proportion of children with vs. without OAS were sensitized to egg whites (36.4% vs. 25.3%) and milk (33.3% vs. 23.4%).
Skin prick testing at age 3 years also revealed that more children with vs. without OAS were sensitized to egg (14.3% vs. 0.7%; P < .001), milk (5.6% vs. 0; P = .002), peanut (5.6% vs. 0.1%; P = .006) and grass (5.6% vs. 0.4%; P = .019).
Children with AR in the full study population had higher mean and gestational ages as well as greater prevalence of parental history of allergic disease, comorbid atopy, asthma, AD and OAS compared with those who did not have AR.
The researchers found a significant association between OAS and food allergy among the children with AR (aOR = 2.971; 95% CI, 1.159-7.615) but not between OAS and AD, AR or recurrent wheeze.
Additionally, among children with AR, sensitization to milk or egg white based on serum-specific IgE at age 1 year, as well as atopy and sensitization to milk, egg or peanut at age 3 years, were considered risk factors for developing OAS.
Although AD and food allergy are potential risk factors for OAS, the researchers found that food allergy had a significant direct effect on OAS among children with AR (direct effect estimate, 1.1; 95% CI, 0.21-1.99).
The researchers noted that OAS incidence varies based on the environment, plant cultivation practices, ethnic groups and regional differences but, still, young children with a history of food allergy or sensitization, particularly those with AR, should be monitored for OAS. Also, the researchers said, further studies are needed to determine the mechanisms of OAS.
Perspective
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The cross-reactivity between pollen and food allergens can result in OAS, especially among those who are already sensitized. Previous studies have shown that children with early allergies generally have a higher risk for having allergies in later childhood as well, so this study supports the literature.
The authors found school-age OAS to be more prevalent among children with comorbidities, such as current AD, AR, food allergy and atopy. However, the association between early childhood allergic disease and school-age OAS among those with current AR was only significant for early food sensitization and food allergy.
It is important to note, though, that the 95% CIs for the association with early food sensitization were very large. Furthermore, the researchers did not find an association between early childhood inhalant allergen sensitization and risk for school-age OAS, which was quite surprising.
Because this was a population-based study, the number of OAS cases was low (n = 44), suggesting that there may have been an insufficient sample size to detect associations. Replication of findings in a larger population-based study, then, is required.
Doctors and parents of children with early childhood food sensitization or allergy may use these results to closely monitor symptoms of OAS in school age, especially if their patients/children also have AR.
Besides validation, future research should explore the mechanisms underlying early childhood food allergy and school-age OAS so appropriate treatments can be developed.
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